Overheating Question

[jtrapani]

Truck: 74 k5, 383, T350 trans. I'm in AZ right now.

My truck is overheating and I don't know why. Coolant level is good. Mix is correct. Just replaced the Thermostat. Water pump is working. I pull the radiator cap and I can see the fluid flowing, I tap the throttle and flow increases. Question: Can the radiator be gummed up in a way that it doesn't cool properly but will still allow good flow? I think its an original radiator.

Also, the engine did get up to 220 degrees. How bad is that? And when It gets warm (200 degrees, which is where I normally turn it off and let it cool) it starts to ping and rattle. Like its pre detonating. what is that rattle?

Thanks guys. I'm thinking that I'll try a radiator flush first and if that doesn't work, replace with a 3 row Al radiator. Is that a good fix maybe?

 

[doonjumper]

Do you have a clutch fan? Are those the temp's while idling or driving down the road?

 

[British Slave]

Do you have the fan shroud in good condition?

 

[jtrapani]

Sorry. Forgot about the fan and shroud. The shroud is in good shape. Clutch fan is working. And the temps are while driving. I haven't hit stop and go traffic but I think it would overheat instantly if I did.

 

[British Slave]

Timing?

 

[6.2Blazer]

Regarding temperatures, 220 itself shouldn't cause any issues with an engine and 200 is simply factory operating temp for a lot of engines. Now if the engine is setup where it is right on the verge of pre-detonation (pinging) when it is running cooler (caused by timing, compression ratio, etc...) than it could start pinging when it reached the higher engine temps.

Also check the outside of the radiator for any blockage. I know you said currently in AZ so pretty dry, but have you been in the mud any time in the recent past? It can be hard to see on the outside but the fins will be packed with dirt and will cause overheating while driving, but is usually fine at idle.

Also, typically overheating at highway speeds means there is something else wrong besides the fan or shroud since these items are meant to help during low speed opertion.

 

[jtrapani]

I think the fan isn't working right. I can spin it really easily when the truck is off. So I'm gonna replace the fan clutch and see if that helps at all. I've got a 3 core radiator. So I'll replace that next if I still have the problem.

As far as the Pre detonation, Its tuned for colorado at 5300 ft elevation. So I've sure that its running lean down here. I'll keep ya'll posted if you care to see how this turns out. Thanks for the ideas.

 

[British Slave]

Can you spin the fan when it's hot? Any signs of oil leakage on the fan?

 

[broncoman6524]

Serpentine or V-belts?

If you converted from V-belts to serpentine, did you swap water pumps? They're opposite rotations.


Thermostat installed right way? If it's upside down, it won't work quite right.

 

[jtrapani]

So the fan was working, but apparently not enough. I replace the fan clutch and the new one draws in way more airflow. Truck only gets up to 180 now. So I think that was the problem. I've got a 3 core radiator with a very minor leak so I know that I need to replace that. I think it might be the original.